Instrument Landing System(ILS)

By: Steven StenstromGeorge Mason University

Instrument Landing System• History of IFR landing procedures

before development if ILS

• What’s it used for?

• How it works

• Why it’s so important

• Future plans for ILS system

History of IFR Landing Procedures

• Until the mid-1950’s, only visual landing procedures were possible

• 1958-First IFR landing system developed

• 1966-First ILS system developed and tested at Edwards AFB in Mojave, CA

• 1968-First ILS applications installed at major airports

• 1974-ILS systems mandated by FAA for at least two major runways at all Regional, and International Airports.

What It’s Used For• Aid aircraft to a runway

touchdown point in IFR conditions

• Aid larger aircraft (ex. Boeing 747,777) to land on a designated runway touchdown point(VFR, IFR)

• Allow for use of new Autoland systems!

MD-80 aircraft taking off over Glide-Slope equipment

How does it work?

• VHF Frequency transmits radar signal and intensity data to ILS Signal Deciphering and Display Computer

• Localizer signal transmitted in direction opposite of runway to horizontally guide aircraft to touchdown point

• Glide-Slope signal transmitted at an angle of 7.5-10 degrees into sky to define vertical descent path to runway touchdown point

• On-board antenna system located in aircraft radome receives radar and VHF signals and sends it to on-board ILS computer

• Signal data is then displayed on instrument panel gauge which maps the directional, and descent path to the runway

On-board ILS gauge from a Boeing 747-400 aircraft

The Signal Transmission System

VHF Glide-Slope Antenna's